HOW TO KNOW THE FRESH-WATER ALGAE 



239a (221) Plants macroscopic; embedded in soft mucilage; a main axis 

 with whorls of branches giving the thallus a beaded effect that 

 is visible to the unaided eye. Eig. 173. . . . BATRACHOSPERMUM 



Fig. 173. a, Batiachospermum mo- 

 niliforme Roth, habit of plant; 

 b, portion of thallus showing 

 small antheridial cells at tips of 

 branches; c, B. vagum (Roth) 

 Ag., antheridial branch in detail; 

 d, B. Boryanum Sirod., carpo- 

 gonial branch with 2 male cells 

 attached to trichogyne of the 

 carpogonium (female organ). 



This genus belongs to the red 

 algae (Rhodophyta) although it 

 shows none of the red color char- 

 acteristic of this group of algae as 

 they occur in the ocean. The ma- 

 croscopic thalli, highly branched 

 and beaded in appearance, en- 

 a cased in copious mucilage make 



Figure 173 these plants easily identified. The 



thallus may be gray-green or blue- 

 green, or olive in color. B. vagum 

 is perhaps the most common species in this country, often occurring 

 in large patches over stones in flowing water. Some species prefer 

 quiet water and are to be sought in Sphagnum bog pools. Micro- 

 scopically it is one of the finest appearing genera of fresh water algae. 



239b Plants microscopic, or if macroscopic, not showing whorls of 

 branches 240 



240a Filaments uniseriate below, becoming multiseriate above with 

 cells brick-like in shape and arrangement; cells adjoined. See 

 Fig. 157 SCHIZOMERIS 



240b Filaments multiseriate throughout; cells not adjoined but arranged 

 in irregular linear series within a gelatinous strand to form a 

 false filament. See Fig. 45 PALMODICTYON 



110 



